1. Field of the Invention
The present invention relates to a compact and large capacity chip type laminated ceramic capacitor and a method for mounting it.
2. Discussion of Background
Laminated ceramic capacitors in the prior art are designed to ensure that the internal electrodes overlap over the largest possible area in order to achieve a larger electrostatic capacity within a limited volume.
Laminated ceramic capacitors in the known art are mounted in such a manner that the internal electrodes are placed parallel to the circuit pattern surface of a printed board or the like to assure sufficient stability (see Japanese Unexamined Patent Publication No. 181033/1996, for instance). However, the printed board becomes thermally expanded and distorted due to heat applied during soldering and the like. During the cooling cycle after the soldering is completed, on the other hand, the printed board undergoes thermal contraction and becomes distorted. Such a distortion may result in cracks forming in the dielectric ceramic body. If there is a crack formed in the dielectric ceramic body, the internal electrodes may become cracked, disconnected or the like. Thus, there is a concern in regard to this mounting method that the electrostatic capacity of the laminated ceramic capacitor may degrade, reducing the insulation resistance.
As a means for lessening the thermal distortion occurring during soldering, laminated ceramic capacitors that feature a structure in which the corners of the front end sides of the internal electrodes are formed in an arc have been proposed (see Japanese Examined Patent Publication No. 1875/1996, Japanese Examined Utility Model Publication No. 14456/1988, Japanese Unexamined Patent Publication No. 181033/1996 and Japanese Unexamined Utility Model Publication No. 92624/1992, for instance).
While this type of laminated ceramic capacitor is effective to a certain degree in reducing the residual stress caused by thermal shock during soldering and preventing degradation of performance caused by cracks, it does not completely eliminate the problem discussed above. Furthermore, since the area over which the internal electrodes overlap is reduced, another problem arises in that the electrostatic capacity that can be achieved is greatly reduced.